How to execute string containing function name AND parameters?

Question

In javascript, I have a string like this:

"doSomething('param1','param2')"

And I want to execute it. I am aware that I could normally use

window['doSomething']('param1', 'param2');

But that only works if my function name is separate from the arguments. In my case they are already combined. I think I can use eval() but the consensus seems to be that it should be avoided. Is there another way?

EDIT: To answer the request for more info: I am using this string like this:

<a id="YesButton" onclick="closeModalView_Yes("doSomething('param1','param2')")">

Where closeModalView_Yes will close the modal yes/no window and then execute the given function, although at times I may pass it doSomethingElse(param1) which only takes one parameter.

If you know what's in the string and won't be surprised ever, just use eval. I mean, you can't ever allow a user to assign the string's value. — user2625787
– user2625787, Commented Jul 31, 2013 at 19:47
How did you get that string, and why? Can't you make it an array ['doSomething', 'param1' 'param2']? — Bergi
– Bergi, Commented Jul 31, 2013 at 20:01
Why don't you pass a callback to closeModalView_Yes instead? Something like closeModalView_Yes(function () { doSomething('param1','param2'); }). — Felix Kling
– Felix Kling, Commented Jul 31, 2013 at 20:29

oleq · Accepted Answer · 2013-07-31 20:36:50Z

1

Use eval, just like:

eval( "console.log( 'hey', 'here I am' )" );

However eval is pretty dangerous and it's not recommended.

If you can (still we don't have much info about your case), render your JavaScript between <script> tags in your template, making it a "regular code", much easier to debug.

Also a good practice is to pass data (i.e. with JSON) rather than code. Try rethinking your logic or provide additional information.

edited Jul 31, 2013 at 20:36

answered Jul 31, 2013 at 19:54

oleq

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4 Comments

Felix Kling Over a year ago

With respect to "security", there is no difference between using eval or using a script element to execute the code though.

oleq Over a year ago

@FelixKling In terms of security - not much. In terms of debugging - hell yes! ;)

Felix Kling Over a year ago

I agree. But since you mentioned both in the same paragraph it sounded like script was safer. Just wanted to clarify that :)

oleq Over a year ago

@FelixKling Agreed. Fixed the answer to avoid misunderstanding.

Bergi · Accepted Answer · 2013-07-31 20:38:42Z

<a id="YesButton" onclick="closeModalView_Yes("doSomething('param1','param2')")">

You really shouldn't pass that as a string, but as a function:

closeModalView_Yes(function(){ doSomething('param1','param2'); });

together with

function closeModalView_Yes(callback) {
    // do whatever needs to be done to close the window
    // and after that
    callback();
}

Btw, with your current approach the HTML is not even valid, it would need to be

<a id="YesButton" onclick="closeModalView_Yes(&quot;doSomething('param1','param2')&quot;)">
<!--                                          ^^^^^^                              ^^^^^^ -->

You could've avoided that by registering the event via javascript instead of inline attributes.

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